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<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="xmlsec-notes-keys-manager-sign-enc"></a>Using keys manager for signatures/encryption.</h2></div></div></div>
<p>Instead of specifiying signature or encryption key in the 
	corresponding context object (<em class="structfield"><code>signKey</code></em> 
	member of <a class="link" href="xmlsec-xmldsig.html#xmlSecDSigCtx" title="struct xmlSecDSigCtx">xmlSecDSigCtx</a> 
	structure or <em class="structfield"><code>encKey</code></em> member of 
	<a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtx" title="struct xmlSecEncCtx">xmlSecEncCtx</a> structure), 
	the application can use keys manager to select the
	signature or encryption key. This is especialy useful
	when you are encrypting or signing something with a session key
	which is by itself should be encrypted. The key for the 
	session key encryption in the 
	<a class="ulink" href="" target="_top">&lt;EncryptedKey/&gt;</a>
	node could be selected using
	<a class="ulink" href="" target="_top">&lt;dsig:KeyName/&gt;</a> 
	node in the template.
	</p>
<p>
	     </p>
<div class="example">
<a name="id-1.2.10.4.3.1"></a><p class="title"><b>Example 17. Encrypting file using a session key and a permanent key from keys manager.</b></p>
<div class="example-contents">
<pre class="programlisting">
/**
 * load_rsa_keys:
 * @key_file:		the key filename.
 *
 * Creates default keys manager and load RSA key from #key_file in it.
 * The caller is responsible for destroing returned keys manager using
 * @xmlSecKeysMngrDestroy.
 *
 * Returns the pointer to newly created keys manager or NULL if an error
 * occurs.
 */
xmlSecKeysMngrPtr 
load_rsa_keys(char* key_file) {
    xmlSecKeysMngrPtr mngr;
    xmlSecKeyPtr key;
    
    assert(key_file);
    
    /* create and initialize keys manager, we use a default list based
     * keys manager, implement your own xmlSecKeysStore klass if you need
     * something more sophisticated 
     */
    mngr = xmlSecKeysMngrCreate();
    if(mngr == NULL) {
	fprintf(stderr, "Error: failed to create keys manager.\n");
	return(NULL);
    }
    if(xmlSecCryptoAppDefaultKeysMngrInit(mngr) &lt; 0) {
	fprintf(stderr, "Error: failed to initialize keys manager.\n");
	xmlSecKeysMngrDestroy(mngr);
	return(NULL);
    }    
    
    /* load private RSA key */
    key = xmlSecCryptoAppKeyLoad(key_file, xmlSecKeyDataFormatPem, NULL, NULL, NULL);
    if(key == NULL) {
        fprintf(stderr,"Error: failed to load rsa key from file \"%s\"\n", key_file);
        xmlSecKeysMngrDestroy(mngr);
        return(NULL);
    }

    /* set key name to the file name, this is just an example! */
    if(xmlSecKeySetName(key, BAD_CAST key_file) &lt; 0) {
        fprintf(stderr,"Error: failed to set key name for key from \"%s\"\n", key_file);
        xmlSecKeyDestroy(key);	
	xmlSecKeysMngrDestroy(mngr);
	return(NULL);
    }
	
    /* add key to keys manager, from now on keys manager is responsible 
     * for destroying key 
     */
    if(xmlSecCryptoAppDefaultKeysMngrAdoptKey(mngr, key) &lt; 0) {
        fprintf(stderr,"Error: failed to add key from \"%s\" to keys manager\n", key_file);
        xmlSecKeyDestroy(key);
        xmlSecKeysMngrDestroy(mngr);
        return(NULL);
    }

    return(mngr);
}

/**
 * encrypt_file:
 * @mngr:		the pointer to keys manager.
 * @xml_file:		the encryption template file name.
 * @key_name:		the RSA key name.
 *
 * Encrypts #xml_file using a dynamicaly created template, a session DES key 
 * and an RSA key from keys manager.
 *
 * Returns 0 on success or a negative value if an error occurs.
 */
int 
encrypt_file(xmlSecKeysMngrPtr mngr, const char* xml_file, const char* key_name) {
    xmlDocPtr doc = NULL;
    xmlNodePtr encDataNode = NULL;
    xmlNodePtr keyInfoNode = NULL;
    xmlNodePtr encKeyNode = NULL;
    xmlNodePtr keyInfoNode2 = NULL;
    xmlSecEncCtxPtr encCtx = NULL;
    int res = -1;
    
    assert(mngr);
    assert(xml_file);
    assert(key_name);

    /* load template */
    doc = xmlParseFile(xml_file);
    if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
	fprintf(stderr, "Error: unable to parse file \"%s\"\n", xml_file);
	goto done;	
    }
    
    /* create encryption template to encrypt XML file and replace 
     * its content with encryption result */
    encDataNode = xmlSecTmplEncDataCreate(doc, xmlSecTransformDes3CbcId,
				NULL, xmlSecTypeEncElement, NULL, NULL);
    if(encDataNode == NULL) {
	fprintf(stderr, "Error: failed to create encryption template\n");
	goto done;   
    }

    /* we want to put encrypted data in the &lt;enc:CipherValue/&gt; node */
    if(xmlSecTmplEncDataEnsureCipherValue(encDataNode) == NULL) {
	fprintf(stderr, "Error: failed to add CipherValue node\n");
	goto done;   
    }

    /* add &lt;dsig:KeyInfo/&gt; */
    keyInfoNode = xmlSecTmplEncDataEnsureKeyInfo(encDataNode, NULL);
    if(keyInfoNode == NULL) {
	fprintf(stderr, "Error: failed to add key info\n");
	goto done;		
    }

    /* add &lt;enc:EncryptedKey/&gt; to store the encrypted session key */
    encKeyNode = xmlSecTmplKeyInfoAddEncryptedKey(keyInfoNode, 
				    xmlSecTransformRsaOaepId, 
				    NULL, NULL, NULL);
    if(encKeyNode == NULL) {
	fprintf(stderr, "Error: failed to add key info\n");
	goto done;		
    }

    /* we want to put encrypted key in the &lt;enc:CipherValue/&gt; node */
    if(xmlSecTmplEncDataEnsureCipherValue(encKeyNode) == NULL) {
	fprintf(stderr, "Error: failed to add CipherValue node\n");
	goto done;   
    }

    /* add &lt;dsig:KeyInfo/&gt; and &lt;dsig:KeyName/&gt; nodes to &lt;enc:EncryptedKey/&gt; */
    keyInfoNode2 = xmlSecTmplEncDataEnsureKeyInfo(encKeyNode, NULL);
    if(keyInfoNode2 == NULL) {
	fprintf(stderr, "Error: failed to add key info\n");
	goto done;		
    }
    
    /* set key name so we can lookup key when needed */
    if(xmlSecTmplKeyInfoAddKeyName(keyInfoNode2, key_name) == NULL) {
	fprintf(stderr, "Error: failed to add key name\n");
	goto done;		
    }

    /* create encryption context */
    encCtx = xmlSecEncCtxCreate(mngr);
    if(encCtx == NULL) {
        fprintf(stderr,"Error: failed to create encryption context\n");
	goto done;
    }

    /* generate a Triple DES key */
    encCtx-&gt;encKey = xmlSecKeyGenerate(xmlSecKeyDataDesId, 192, xmlSecKeyDataTypeSession);
    if(encCtx-&gt;encKey == NULL) {
        fprintf(stderr,"Error: failed to generate session des key\n");
	goto done;
    }

    /* encrypt the data */
    if(xmlSecEncCtxXmlEncrypt(encCtx, encDataNode, xmlDocGetRootElement(doc)) &lt; 0) {
        fprintf(stderr,"Error: encryption failed\n");
	goto done;
    }
    
    /* we template is inserted in the doc */
    encDataNode = NULL;
        
    /* print encrypted data with document to stdout */
    xmlDocDump(stdout, doc);
    
    /* success */
    res = 0;

done:    

    /* cleanup */
    if(encCtx != NULL) {
	xmlSecEncCtxDestroy(encCtx);
    }

    if(encDataNode != NULL) {
	xmlFreeNode(encDataNode);
    }
        
    if(doc != NULL) {
	xmlFreeDoc(doc); 
    }
    return(res);
}

		</pre>
<p><a class="link" href="xmlsec-encrypt-with-session-key.html#xmlsec-example-encrypt3" title="encrypt3.c">Full program listing</a></p>
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